County ZIP codes · Missouri · FIPS 29221
Washington County, MO ZIP Codes
Washington County, Missouri has 16 ZIP codes (Census 2020 ZCTA-county file; GeoNames postal codes, October 2026), all residential. 10 of the residential ones lie mainly in Washington County and 6 mainly in a neighboring county; 11 cross the county line. Median household income ranges from $41,984 in 63624 (Bismarck) to $70,824 in 63020 (De Soto) (Census Bureau, ACS 2020-2024).
- ACS2020-24
- Census2020
Where are the ZIP codes of Washington County?
Source: U.S. Census Bureau, 2020 ZCTA cartographic boundaries; ACS 2020-2024 5-year estimates (B19013).
How different are its ZIP codes?
The middle half of its ranked ZIP codes (1,000+ people living in households) report median household incomes between $50,277 and $65,050.
They carry 16 postal town names.
Source: U.S. Census Bureau, ACS 2020-2024 5-year estimates (B19013).
All 16 residential ZIP codes in Washington County
10 ZIP codes lie mainly in Washington County; 6 more reach into it from a neighboring county and follow the first table.
| In this county | ||||||
|---|---|---|---|---|---|---|
| 63664 | Potosi | 9,693 | 34 | $61k | $125k | 100% |
| 63630 | Cadet | 4,006 | 59 | $53k | $150k | 93% |
| 63660 | Mineral Point | 2,784 | 79 | $51k | $120k | 100% |
| 63648 | Irondale | 1,858 | 59 | $52k | $100k | 93% |
| 63071 | Richwoods | 1,113 | 29 | $45k | $123k | 100% |
| 63622 | Belgrade | 764 | 17 | $32k | – | 100% |
| 63626 | Blackwell | 588 | 28 | $83k | $182k | 81% |
| 63030 | Fletcher | 557 | 70 | $91k | $183k | 94% |
| 63631 | Caledonia | 544 | 13 | $74k | $128k | 65% |
| 63674 | Tiff | 48 | 17 | – | – | 100% |
Partly in Washington County
| In this county | ||||||
|---|---|---|---|---|---|---|
| 63080 | Sullivan | 13,124 | 53 | $67k | $183k | 39% |
| 63624 | Bismarck | 3,447 | 57 | $42k | $90k | 29% |
| 65441 | Bourbon | 5,028 | 30 | $65k | $204k | 26% |
| 65565 | Steelville | 4,845 | 18 | $50k | $163k | 11% |
| 63020 | De Soto | 20,166 | 135 | $71k | $186k | 6% |
| 63628 | Bonne Terre | 16,416 | 137 | $64k | $189k | 6% |
Source: U.S. Census Bureau, ACS 2020-2024 5-year estimates; county shares by land area (Census 2020 ZCTA-county relationship file).
Which ZIP codes cross the county line?
11 ZIP codes of Washington County extend into another county. A ZIP code follows mail routes, not county borders.
| ZIP | In Washington | Elsewhere |
|---|---|---|
| 63020 | 6% | Jefferson County 94% |
| 63628 | 6% | St. Francois County 84%; Ste. Genevieve County 8%; Jefferson County 2% |
| 63080 | 39% | Franklin County 57%; Crawford County 4% |
| 65441 | 26% | Crawford County 73%; Franklin County 1% |
| 65565 | 11% | Crawford County 81%; Iron County 8% |
| 63630 | 93% | St. Francois County 7% |
| 63624 | 29% | St. Francois County 55%; Iron County 16% |
| 63648 | 93% | St. Francois County 7% |
| 63626 | 81% | St. Francois County 19% |
| 63030 | 94% | Jefferson County 6% |
| 63631 | 65% | Iron County 35% |
Source: U.S. Census Bureau, 2020 ZCTA-county relationship file (shares of land area).
Which first three digits do Washington County's ZIP codes use?
The first three digits of a ZIP code name the sectional center, the mail processing plant that sorts it. Washington County's ZIP codes use 4 prefixes: 630, 636, 654 and 655.
| Prefix | Sectional center | Here | All codes |
|---|---|---|---|
| 630 | St Louis, MO (SCF 630) | 4 | 65 |
| 636 | St Louis, MO (SCF 630) | 10 | 37 |
| 654 | Springfield, MO (SCF 656) | 1 | 29 |
| 655 | Springfield, MO (SCF 656) | 1 | 33 |
Source: U.S. Postal Service, labeling list L005 (3-digit ZIP Code prefix groups, SCF sortation), effective October 1, 2026.